Seroquel - How long does it take for seroquel to take effect?

Hi, MarySue! Some people begin feeling some positive effects at around four weeks, but it may take as long as 6-8 weeks to reach maximum therapeutic blood levels. You should however feel some mild side effects such as drowsiness and headache almost right away. They are generally transient, lasting only a few days to a few weeks,
Best wishes, WCV

Good answer from Wildcat; But if they are giving this to you for sleep many people say it works much sooner.BUT for all the other things it can do it's all on WildcatVets post.